A comparative study: the impact of different lipid extraction methods on current microalgal lipid research

Yan Li,Wael Ghafor,Simon Tannock,Kristofer J Thurecht,Forough Ghasemi Naghdi,Peer M Schenk,Tania Adarme-Vega,Sourabh Garg

doi:10.1186/1475-2859-13-14

Abstract

Microalgae cells have the potential to rapidly accumulate lipids, such as triacylglycerides that contain fatty acids important for high value fatty acids (e.g., EPA and DHA) and/or biodiesel production. However, lipid extraction methods for microalgae cells are not well established, and there is currently no standard extraction method for the determination of the fatty acid content of microalgae. This has caused a few problems in microlagal biofuel research due to the bias derived from different extraction methods. Therefore, this study used several extraction methods for fatty acid analysis on marine microalga Tetraselmis sp. M8, aiming to assess the potential impact of different extractions on current microalgal lipid research. These methods included classical Bligh & Dyer lipid extraction, two other chemical extractions using different solvents and sonication, direct saponification and supercritical CO2 extraction. Soxhlet-based extraction was used to weigh out the importance of solvent polarity in the algal oil extraction. Coupled with GC/MS, a Thermogravimetric Analyser was used to improve the quantification of microalgal lipid extractions. Among these extractions, significant differences were observed in both, extract yield and fatty acid composition. The supercritical extraction technique stood out most for effective extraction of microalgal lipids, especially for long chain unsaturated fatty acids. The results highlight the necessity for comparative analyses of microalgae fatty acids and careful choice and validation of analytical methodology in microalgal lipid research.

Highlights

Since the concept of using algae to make fuels was firstly discussed in the 1940s [1], a major focus for research, development and commercialization has become the cultivation of algae for the production of oil-based products, in particular biodiesel through lipid transesterification
The impact of solvent polarity on lipid extraction The results obtained for Soxhlet extraction of microalgal lipids showed a significant difference in extraction efficiency between hexane and the mixture of hexane and ethanol in both, total lipids and total fatty acid methyl esters (FAME), as well as each individual fatty acid (P < 0.05, Figure 1A and B)
Regardless of the biological difference of these algal species and its resulting different lipid class compositions, the contradiction is possibly related to the different proportions of hexane:ethanol in the mixture (3:1 vs. 1:1)

Summary

Introduction

Since the concept of using algae to make fuels was firstly discussed in the 1940s [1], a major focus for research, development and commercialization has become the cultivation of algae for the production of oil (lipid)-based products, in particular biodiesel through lipid transesterification. Algal lipids can be divided into two major types: polar lipids such as phospholipids and glycolipids, and neutral/nonpolar lipids such as mono-, di- and tri-acylglycerides and carotenoids based on their physiochemical characteristics [2,3]. Some of these substances have been intensively. An appropriate technique of cell disruption is a prerequisite [7,8], the efficient extraction of lipids is highly dependent on the polarity of the organic solvent or solvent mixture used [9,10]. Comparative economics of technical and physiochemical methods for oil extraction have not been accomplished on microalgae cells

Methods

Results

Conclusion